Preheat the oven to 375°F. Lightly spray a doughnut tin with cooking spray and set aside.

In a large bowl, whisk together the flour, brown sugar, cocoa powder, salt, baking powder and baking soda until well combined.

In another bowl, whisk together the egg, sour cream, oil, milk and vanilla until smooth and well combined.

Add this mixture to the dry ingredients and stir until just combined. The batter will be quite thick.

Spoon or pipe the batter into the prepared doughnut tin and bake for 8-10 minutes or until the doughnuts spring back when lightly pressed.

Let them cool for 5 minutes in the tin and then turn them out onto a cooling rack to cool completely.

Prepare the glaze by whisking together the powdered sugar, milk, peppermint extract and food coloring (if using) until smooth and well combined.

Start with 2 tablespoons of milk and add a bit more if needed to thin it to the desired consistency.

Dip the doughnuts into the glaze and add sprinkles if you like. Let the glaze set before serving.